Mark Dummett, business and human rights researcher at AI, said: “Consumers of electric vehicles are concerned about the environment, they’re ethically aware... So we feel that understandably they would expect these companies to live up to international standards and be able to trace these supply chains back.

“Any company which is using cobalt… all of them, they have a responsibility to map out that supply chain and identify their smelters and find out what steps those smelters are taking to avoid child labour.”

AI said it used publicly available company records to trace the supply chains of these automotive companies to Chinese-owned Huayou Cobalt, through two large battery manufacturers.

The charity claimed none of the companies had shown they had identified cobalt refiners or smelters in their supply chains or conducted their own assessments on the smelter’s safeguards, as required by the OECD.

Cobalt is a key component in most lithium-ion batteries, and can be found in consumer goods including cars, phones and laptops. Half of the world’s cobalt comes from the Democratic Republic of Congo (DRC), and 20% of that is extracted from artisanal mines, often under poor labour conditions.

AI wrote to all five companies to ask what safeguards were in place in their cobalt supply chains.

BMW responded it was aware of risks around sourcing cobalt from DRC and said its tier one battery supplier had “assured us that there are no human rights violations” in any of its cobalt supply chains.

BMW also said it had been working with suppliers to identify smelters, but declined to disclose the names of these smelters.

Fiat-Chrysler said it had contacted its tier one supplier after receiving AI’s letter and was told its cobalt supply chains were monitored. Fiat-Chrysler does not currently have any programmes in place to identify cobalt smelters and refiners in its supply chain.

Both deny any connection to Huayou Cobalt.

GM and Tesla did not respond to the letter, and Renault-Nissan said it would reply “at the earliest possible time”, AI said.

In a statement GM said it had “a zero-tolerance policy... against the use of child labour in the supply of goods and services to GM and its subsidiaries”. It also said LG, its tier one battery supplier, had “instituted a process with its tiered cobalt supplier to prevent the use of cobalt from the [DRC] in GM’s battery production.”

A spokeswoman from Tesla said there was very little cobalt in its battery cells, and that Tesla had received certifications from “the relevant producers of our main Panasonic supply chain that all raw materials are produced in a responsible manner”.

She added: “The LG Chem supply chain that is used for the cells that Tesla purchases from them does not include cobalt mined in the DRC.”

A spokeswomen for Renault said its battery supplier, also LG Chem, certified to Renault it did not source its cobalt from the DRC.

A spokesman for Fiat-Chrysler said they had “no other comment to add to what has already been provided to Amnesty”.